Ghibe river basin in Ethiopia : present situation of trypanocidal drug resistance in Trypanosoma congolense using test in mice and PCR-RFLP

Abstract:

A cross-sectional study was carried out in the Ghibe valley from August to October 2010.
411 head of cattle were sampled in eight villages for buffy coat examination (BCE) and blood
spots were collected from each animal for trypanosomose diagnosis by 18S-PCR-RFLP and
diminazene aceturate (DA) resistance by Ade2-PCR-RFLP. Three villages were selected in a
zone where trypanosomosis control operations are currently on-going whereas the other 5
villages were located outside these control operations. Twenty-four samples (5.84%) were
diagnosed positive for Trypanosoma congolense by BCE and injected in mice for further
characterization. Twelve of those isolates successfully multiplied in mice and were tested
by an in vivo mouse test for diminazene (DA) (10 and 20 mg/kg B.W.) and isometamidium
(ISM) (1 mg/kg B.W.) resistance. All were shown to be resistant to both drugs at all doses. The
use of the Ade2-PCR-RFLP on these isolates confirmed their DA-resistance profile. Seventythree
of the collected blood spots (17.8%) were diagnosed positive for T. congolense by
18S-PCR-RFLP of which 37 (50.7%) gave amplification products with the Ade2-PCR-RFLP.
Here, 35 (94.6%) showed a resistant profile, 1 (2.7%) a sensitive profile and 1 (2.7%) a mixed
profile. The data were analysed by logistic regression model and the relapsing time in mice
tests was assessed using the Cox regression model. There was no significant intervention
effect (P = 0.83) with odds ratio equal to 1.21 when using the BCE data. 18S-PCR-RFLP test
also showed no significant intervention effect (P = 0.60) with odds ratio equal to 1.43. The
hazard ratio of getting parasitaemic after treatment with DA at 20 mg/kg B.W. compared to
the control group was 0.38 which differs significantly from one (P < 0.001). Relapsing time
after treatment with DA 10 mg/kg B.W. or ISM 1 mg/kg B.W. was also significantly longer
than the prepatent period of the control group. The situation of drug resistance in the Ghibe
valley is further discussed.